The present disclosure relates to the field of heat transfer, and more particularly to the provision of thermal isolation between a volume of high-temperature fluid and a vessel that contains the high-temperature fluid. There are applications that require use of a high-temperature fluid to store heat and to deliver the heat for use in an application, such as electric power generation, control of a chemical synthesis reaction, extraction of ore, high-efficiency electric batteries, secondary recovery of oil in a producing stratum, or heat transfer and neutronics in a critical or subcritical fission core. In some of the applications, the high-temperature fluid with most beneficial properties is molten salt. For many of the applications, the performance and energy efficiency of the process improves with temperature up to 800° C. For such applications, the metals ordinarily used in vessels and piping cannot reliably operate in contact with molten salt at temperatures above 600° C. Such applications are typically limited by the strength of metals and alloys at high temperature and by chemical corrosion of the metals or alloys. At these high temperatures, conventional structural metals lose their strength and metal surfaces corrode at a significant rate. Metal alloys containing a high fraction of nickel are capable of operating reliably at 800° C. while resisting corrosion. However, such alloys are very expensive and would not be affordable as the material of a tank and piping for many of the applications cited above.